I got build 22000.1 on the 1st day (24 june) from Windows Update in the Dev channel.
Yes it was updated by Windows Update to 22000.51 a few hours later.
And I had to fix an incorrectly registered version for one file of .Net 4, using "SFC /SCANNOW": it was forgotten and stayed at the version shipped for 22000.1.
So I really have had the two builds !
I suggest to all viewers in this thread to run "SFC /SCANNOW" because there are possible versioning problems: this command must be run from an administrator console, it should fix it. You'll need to reboot Windows after that, and run again "SFC /SCANNOW" to check that all is OK (look also in the "\Windows\Logs\CBS\CBS.log" with a text editor to see if there are other fixes: look directly at end of the log, you'll see if all repairs were correctly applied and all files were properly loaded from the Microsoft updates site).
The versioning problem may explain why build 22000.51 was published just a few hours after 22000.1, but we have no details from Microsoft about the real reason.